1. Field of the Invention
The present invention relates to a soil compacting device, in particular a vibration plate.
2. Description of the Related Art
Steerable and non-steerable vibration plates are known that can be controlled manually or remotely. Standardly, the vibration plates have an upper mass comprising, inter alia, a drive, e.g. a motor, as well as a lower mass that is coupled to the upper mass and that is capable of oscillatory movement relative to the upper mass. The lower mass is made up essentially of a soil contact plate to which a vibration exciter is fastened. The vibration exciter is driven by the drive of the upper mass, and has for example two imbalance shafts, situated parallel to one another, that are capable of rotation in directions opposite to one another with a positive fit. Each imbalance shaft bears one or more imbalance masses, so that during rotation with a positive fit a resultant force is produced. Depending on the phase position of the imbalance shafts or masses to one another, the direction of the resultant force can be set perpendicular to the axes of the imbalance shafts as desired by the operator. In this way, the vibration plates can be moved at least in the forward direction (main direction) and the backward direction.
In addition, vibration plates are known that are able to travel a curved path or to execute a rotation in place. For this purpose, on one of the imbalance shafts of the vibration exciter the imbalance mass is divided into two mass elements that can be moved separately from one another with respect to their phase position, or the imbalance shaft is divided into two sub-shafts. Given a different orientation of the resultant force that arises in the interaction with the oppositely situated, non-divided imbalance shaft, there arises a yaw moment about a vertical axis of the vibration plate, which causes a rotational movement.
The vibrations produced by the vibration exciter and the interaction with the soil cause the lower mass, in particular its soil contact plate, to execute a kind of wobbling movement on the soil. The wobbling movement effects the actual soil compacting.
In steerable vibration plates, i.e., vibration plates that are capable of rotation or of traveling in a curved path, the vibration exciter must handle three tasks simultaneously or in temporal succession. On the one hand, a propulsive force must be produced in order to move the vibration plate forwards and backwards with sufficient speed. In addition, a compacting effect is to be brought about in order to perform the actual aim of the device, namely soil compacting. Finally, a moment of rotation (yaw moment) is to be produced about the vertical axis of the vibration plate by differently controlling the imbalance masses to the right and to the left of a center plane of the vibration plate.
As a rule, performing these three tasks requires a compromise, so that none of these tasks can be optimally performed. In vibration plates in which only a change of direction is possible, the production of the propulsive force always entails a loss of compacting power. The compacting power is optimal only when the device is at a standstill, when the vibration exciter does not have to produce any propulsive forces. If the third function, i.e., the production of a rotational movement, also has to be performed by the vibration exciter, the compacting efficiency can be significantly reduced, which has a disadvantageous effect on the final result of the work, above all on the time required for compacting.
However, in the area of soil compacting, analogously to the general trend in the construction machine industry, the efficiency of compactors is becoming increasingly important so that compacting work can be performed in the shortest possible time.
Correspondingly, the required machines are becoming larger and heavier, and are therefore becoming more and more difficult to operate manually.
Other soil compacting devices are known in which a plurality of hydraulically operated compacting plates are fastened to a hydraulic bearer, e.g. a tractor-type vehicle standard on construction sites. The vibration plates are used exclusively for soil compacting, while the steering and guiding, as well as the propulsion, are taken over by the tractor vehicle. Such a system can be used in particular for compacting on inclined surfaces, while manually operated or remotely controlled
vibration plates can be guided over inclined surfaces only with great difficulty. However, the vehicle-supported compacting devices have the disadvantage that the wheels often damage the surface of the compacted soil. In addition, the vehicles can be used economically only on large surfaces. Their maneuverability is very limited.
GB 805 643 A and DE 864 263 C each indicate soil compacting devices in which a plurality of vibration plates or stampers are combined by connecting elements to form a larger overall system. A separate drive is allocated to each vibration plate or to each stamper.